Finding heterogeneous catalysts that are superior to homogeneous ones for selective catalytic transformations is a major challenge in catalysis. Here, we show how micropores in metal-organic frameworks (MOFs) push homogeneous catalytic reactions into kinetic regimes inaccessible under standard conditions. Such property allows branched selectivity up to 90% in the Co-catalysed hydroformylation of olefins without directing groups, not achievable with existing catalysts. This finding has a big potential in the production of aldehydes for the fine chemical industry. Monte Carlo and density functional theory simulations combined with kinetic models show that the micropores of MOFs with UMCM-1 and MOF-74 topologies increase the olefins density beyond neat conditions while partially preventing the adsorption of syngas leading to high branched selectivity. The easy experimental protocol and the chemical and structural flexibility of MOFs will attract the interest of the fine chemical industries towards the design of heterogeneous processes with exceptional selectivity.
The introduction of structural defects in metalorganic frameworks (MOFs), often achieved through the fractional use of defective linkers,i se merging as am eans to refine the properties of existing MOFs.T hese linkers,m issing coordination fragments,c reate unsaturated framework nodes that may alter the properties of the MOF.Aproperty-targeted utilization of this approach demands an understanding of the structure of the defect-engineered MOF.W ed emonstrate that full-field X-raya bsorption near-edge structure computed tomography can help to improve our understanding.T his was demonstrated by visualizing the chemical heterogeneity found in defect-engineered HKUST-1 MOF crystals.Anonuniform incorporation and zonation of the defective linker was discovered, leading to the presence of clusters of as econd coordination polymer within HKUST-1. The former is suggested to be responsible,i np art, for altered MOF properties; thereby, advocating for aspatio-chemically resolved characterization of MOFs.
In
this work, acidic oxidation in a biphasic water/octanol system
was applied to mitigate condensation and increase the yields of high-value
aromatic monomers from Kraft lignin, a waste product, and an industrially
relevant feedstock. Biphasic depolymerization (BPD) is a one-pot multistep
technique in which target molecules are protected from degradation
in the reactive aqueous milieu (necessary for the cleavage of β-O-4
bonds as well as the recalcitrant high dissociation energy carbon–carbon
moieties) by an in situ transfer of the products
into the protective octanol phase. The results have shown overall
monomeric yields up to 13 wt % and yields of vanillin up to 7 wt %
(FeCl3 as a catalyst and O2 as an oxidant),
significantly outperforming the previously reported monophasic and
biphasic outcomes for Kraft lignin. In addition to increased yields,
BPD also resulted in an expansion of the product pool from few molecules
typically reported in the literature to 64 aromatic monomers detected
at various concentration levels in the current work. The identified
aromatic alcohols, carbonyl compounds, and carboxylic acids incorporating
varying side chain lengths show potential as green and sustainable
replacements to BTX (benzene, toluene, and xylene) petrochemicals.
BPD as a process coupled mild conversion conditions, cheap oxidants,
and common homogeneous catalysts with an in situ separation
of the products from the reaction mixture to yield excellent results
in converting industrial waste and recalcitrant feedstocks into value.
Cross-coupling reactions are a fundamental tool in the large scale synthesis of pharma-, agro- and fine chemicals. Homogeneous palladium complexes remain the state-of-the-art catalysts even though the use of heterogeneous...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.